Heating furnace



J.CURRAN Nov. 26, 1940.

HEATING FURNACE Filed Sept. 12, 1939 2.22am Ame eon @ardifl, WalesApplication September 12, 1939, Serial No. 294,532

In Great Bri September 20, 1938 a (lie (oi. 283-8) This inventionrelates to heating furnaces and especially to annealing furnaces.

An object of the invention is to provide a device for usefully employingthe heat contained in a charge which has'passed out of the furnace.

This object is effected according to the invention by providing meansfor circulating a stream of gas over the charge which has emerged fromthe furnace proper and passing this gas to the charge awaiting entry tothe furnace over a path exterior to the furnace interior.

By a further feature of the invention damper means are provided toregulate the relative proportions of heated gas reaching the part of anentry chamber through which the charge passes before entering thefurnace which is nearest the furnace door and the part which is nearestthe outer door of the entry chamber. Thermally responsive devices ofknown kind may be provided to operate the damper means in accordancewith the temperature of the circulating gas and to reduce the quantityof gas entering the part of the entry chamber nearest the furnace door,or stop such admission, when the temperature of the gas falls below apredetermined value. Preferably, this feature of the invention isemployed in comunction with means for heating the part of the entrychamber adjacent the furnace door. The charge nearest the furnace doorwill attain a higher temperature than that nearest the outer door of theentry chamber and by passing all or a greater part of the circulatinggas over the.

charge nearestthe outer door when the tempera ture of the circulatinggas falls, the temperature of the charge actually entering the furnacecan be maintained more nearly at a constant desired value, whiletheamount of heat imparted to the cold charge is as great as possible. Inthe case of an annealing furnace maintained at a constant temperatureand where the operation of the conveyer to discharge and load thefurnace occurs at fixed times-the maintenance of the entering charge ata fixed temperature is important.

The heating is preferably electrical and the furnace may be divided intoas many zones or chambers as is desired.

The invention is illustrated by way of example in the accompanyingdrawing, in which- Fig. 1 is a section of the furnace, and

Fig. 2 is a diagram of the electrical circuit for controlling thedampers.

The charge which may be, for example, cartridge cases, is. adapted to bemoved into and through the furnace l by a conveyer 2 driven by drums I9.The furnace is provided with doors 3, t at eachend of the furnace spaceproper and further doors 5, 6 which afiord access to an entry chamber 1and an exit chamber 8 in which the charge rests before entering thefurnace proper and after emerging therefrom respectively. The

doors are counterbalanced by weights 28 suspended by chains Zl passingover pulleys 22, and

are arranged to be opened and closed together to permit the charge to becarried into and through the furnace. A lagged duct 9 isflformed in themasonry of the furnace below the upper run of the conveyer 2, whichcommunicates with the entry and exit chambers through openings it in thefloors thereof. A further lagged duct Hi arranged above the furnaceopens to the upper spaces of the entry and exit chambers, and afan H isarranged in this duct to cause air to pass from the upper part of theentry chamber to the upper part of the exit chamber, over a heatedcharge in this chamber and through theopenings in the floor to theopenings in the floor of the entry chamber, returning over the coldcharge to the fan. The flow of air is indicated by the arrows.

The entry chamber 7 is divided by a door 5A into an inner compartment l2and an outer compartment i3. Access to the compartment l2 M by the hotair from the exit chamber 8 is controlled by pivoted dampers I5 and towhich are operated thermostatically in such a manner that they open orclose simultaneouslyto isolate or connect the compartment H from or withthe compartment 8 in dependence on the temperature of the hot air andthe compartment if. The compartment l2 of the entry chamber is providedwith electrical heating elements l6 similar to the heating elements I!of the furnace proper.

The dampers l5 and It also serve to control the circulation of gas inthe ducts 9 and It. A gas other than air may, of course, be .circulatedwhen desired. I

Referring to Fig. 2, the dampers I5 and i8 (not motor indicateddiagrammatically as a motor at 24. supplied from mains 2'! and 28through contacts 25 and a thermostat C. The arrangement is such ,thatthe dampers I5 and I8 are closed when contacts 25 are in the offposition. Suitable means mesh with pinions 15b and [8b respectively. The

pinions are fixed respectively to the hinged ends of the dampers l5 andI8. The thermostat C-is placed in the compartment l2 and completes a Thecurrent for the solenoid or motor is shown in Fig. 2) are actuated by asolenoid or circuit for opening the dampers I5 and I8, when w thetemperature in compartment I2 is sumciently high, provided the contacts26 are closed. Current forthe heaters i6 is supplied through contacts 25which are operated by a circuit including thermostats A and B situatedrespectively in the chamber 8 and the compartment 12. The

contacts are held in by a circuit including contacts 32 and thermostatB, so that once closed, the contacts 25 remain closed independently ofthe temperature in the chamber 8 until the temperature of thecompartment l2 rises abovea predetermined value. When once opened,however, contacts 25 will not be again closed until the temperature inboth chamber 8 and compartment I2 falls. Opening of the contacts 32causes interlocked contacts 33 to close, thus completing a circuit forclosing contacts 26. Closure of contacts 28 completes a circuit forsupplying the fan H with current by way of the leads 29 and 30.

I claim:

1. A heating furnace having an entry and an exit, an entry chamber,closure means between the entry chamber and the furnace, further closuremeans dividing the entry chamber into a part adjacent to the furnace anda part remote from the furnace, an exit chamber adjacent to the furnaceexit, a duct closed to. the interior of the furnace and connecting thetwo said parts of the entry chamber with the exit chambenmeans forpassing a gas through the duct from the exit chamber to the entrychamber, damper means for controlling the relative proportions. of .thegas reaching the part of the entry chamber adjacent to the furnace andthe part remote from the furnace respectively, and means for controllingthe damper in dependence on the temperature of the part of the entrychamber adjacent to the furnace to reduce the proportion of gas enteringthe part of the entry chamber adjacent to the furnace when thetemperature thereof falls.

2. A heating furnace having an entry and an exit, an entry chamber,closure means between the entry chamber and the furnace. further closuremeans dividing the entry chamber into a part adjacent to the furnace anda part remote from the furnace, an exit chamber adjacent to the furnaceexit, a duct closed to the interior of the furnace and connectingthe-two said parts of the entry chamber with the exit chamber, means forpassing a gas through the duct from the exit chamber to the entrychamber, damper means for shutting off from the said duct the part ofthe entry chamber adjacent to the furnace, and means for actuating saiddamperimeans to shut oi! the part of the entry chamber adjacent to thefurnace when the temperature of the last-named part of the entry chamberfalls below a prede termined value. k

3. A heating furnace having an entry and an exit, an entry chamber,closure means between the entry chamber and the furnace, further closuremeans dividing the entry chamber into a nace, means for closing thedamper means when the temperature of the last-named part of the entrychamber falls below a predetermined value, and means for opening saiddamper means when the temperature of the part of the entry chamberadjacent to the furnace and the temperature of the exit chamber riseabove respective predetermined values.

4. A heating furnace having an entry and an exit, an entry chamber,closure means between the entry chamber and the furnace, further closuremeans dividing the entry chamber into a part adjacent to the furnace anda part remote from thefurnace, an exit chamber adjacent to the furnaceexit, a duct closed to the interior of the furnace and connecting thetwo said parts of the entry chamber with the exit chamber, means forpassing a gas through the duct from the exit I chamber to the entrychamber, damper means for shutting off from the said-duct the part ofthe entry chamber adjacent to the furnace, means for actuating saiddamper means to shut off the part of the entry chamber adjacent to thefurnace when the temperature of the last-named part of the entry chamberfalls below a predetermined value, heating means in the part of theentry chamber adjacent to the furnace, and means for switching saidheating means on when the temperature of the exit chamber and that ofthe part of theve'ntry chamber adjacent to the.

furnace fall below respective predetermined val ues and for maintainingsaid heating means on so long as the temperature of the last-named partofthe entry chamber remains below said lastmentloned predetermined valuethereof.

5. A heatingfurnace as claimed in claim 3 comprising heating means inthe part of the entry chamber adjacent to. the furnace, and means forswitching said heating means on when the temperature of the exit chamberand that of the part of the entry chamber adjacent to the furnace fallbelow said last-mentioned respective predetermined values and formaintaining said heating means on so long as the temperature of thelast-named part of the entry chamber remains below said last-mentionedpredetermined value thereof.

6. A heating furnace as claimed in claim 2 comprising heating means inthe part of the entry chamber adjacent to the furnace, and means forswitching said heating means on when the temperature of the part of theentry chamber adjacent to the furnace falls below a predeter minedvalue.

7. A heating furnace having an entry chamber, an exit chamber, closuremeans between the entry chamber and the furnace, further closure meansdividing the entry chamber into a part adjacent to the furnace and apart remote from -the furnace, an exit chamber adjacent to the furnaceexit, a duct closed to the interior of the furnace and connecting thetwo said parts of the entry chamber with the exit chamber, means forpassing a gas through the duct from the exit chamber to the entrychamber and damper means for controlling, the relative proportions ofgas reaching the part of the entry chamber adjacent to the furnace andthe part remote from the furnace respectively. 3

8. A heating furnace as claimed in claim 7 comprising heating meansin-the part of the entry chamber adjacent to the furnace, and means

